Winston threw passes for the first time in four days, and Koetter said Winston would get all the reps in Friday's practice.
"He's our starter. Jameis will be our starter. He'll be out there," Koetter said with no hesitation. "Jameis threw the ball well today. He threw it well."
Winston suffered the injury on the first series of a loss Sunday to the Arizona Cardinals, when he took a jarring hit from linebacker Chandler Jones and fell hard on his right shoulder. Winston was replaced by backup Ryan Fitzpatrick in the second quarter.
Koetter said earlier this week that there was no structural damage to Winston's shoulder and it was more about pain tolerance than risk of further injury.
"It's not really about passes and making the throws," Winston said. "It's just the pain. That's all. This is a long season. That's the biggest thing -- it's a long season."
This isn't the first time Winston has dealt with a sprained AC joint in his throwing arm. He was almost 100 percent certain of the injury before he even had an MRI this week, and he vowed to not miss a game.
"I had a couple of AC joints that I had to play through, so I'm used to the pain," Winston said. "Every one [of the injuries] is different. I can't tell you about my injuries eight years ago. I can just tell you about this one."
Winston practiced with the team this week, but he did not throw the ball until Friday morning. Fitzpatrick split reps with third quarterback Ryan Griffin on Wednesday and Thursday while Winston simulated throws with his lower body.
During the 30 minutes of practice that were open to the media Friday, Winston threw mostly short-to-intermediate passes. He hit wide receiver DeSean Jackson, tight end Cameron Brate, tight end O.J. Howard and wide receiver Bernard Reedy.
All week long, there were concerns about his velocity. So when Winston threw the ball toward the corner of the end zone as a joke, nearly hitting a group of reporters, it drew a chuckle from Koetter on the field.
"Eh," Koetter said with a smile when asked if was intentional. "No comment."